Harry was trying to figure out where his classmates and friends kept going in the middle of the night, to find out they are going to a club or class for a sex ed type set=up taught by Severus. Harry was never invited, being a virgin, but upon learning about it, starts attending class, with special assignments that match his preference and inexperience. I lost it at a point where Severus and harry hook up and Severus finally takes Harry for his own. Any recollections would be great!